1. Fie1d of the Invention
The invention relates to fuel tanks such as those used with small engines in garden tractors and the like. More particularly, it relates to a venting system used therewith.
2. Background of the Art
Fuel tanks are typically vented to maintain their internal pressure at acceptable levels. Without venting, temperature change, fuel agitation and/or consumption of fuel by the engine, may generate substantial positive or negative pressure within the tank. Such pressure may interfere with the proper delivery of fuel from the fuel tank to the carburetor of the engine during the engine's operation.
The required venting is usually accomplished by means of a venting orifice at the top of the tank. The orifice may be incorporated into the cap used to close the filling port. Alternatively the orifice may be a separate hole in a gauge or the like or simply a slot cut through the cap threads and gasket.
The agitation of the fuel during the operation of the engine, and variations in the attitude of the engine platform which may be a small tractor or the like, makes it desirable that the venting orifice be fitted with a means of limiting the escape of liquid fuel thrown against the vent. The orifice, therefore, is often fitted with a convoluted channel or filter to try to selectively pass vapor but not liquid. Such methods of preventing the escape of liquid fuel are not wholly successful and it is not unusual for small quantities of liquid fuel to escape through or around the fuel cap during operation of the engine. This is especially true when the fuel tank is full. Bidirectional check valves have been tried, but often these can require maintenance and/or exacting manufacturing tolerances.
In any event, even where prior art systems prevent liquid fuel leakage, because the vent is near the top of the tank the user of the engine may be exposed to unpleasant fumes.